The present invention relates to firearms technology. In particular, the present invention concerns a rifle barrel having a bore configuration which projects a projectile in a highly accurate manner by correcting bullet runout without sacrificing muzzle velocity.
Various rifle bore configurations have been disclosed in the industry. Several examples are discussed below.
U.S. Pat. No. 4,527,348, incorporated herein by reference, discloses a gun barrel adapted to be connected to a receiver includes a rifled portion and a smoothbore portion. The rifled portion may have deeper than normal grooves to permit the escape of propellant gases past the bullet. The smoothbore portion includes an increased diameter expansion section, a reduced diameter compression section and an alignment section. Gases expanding past the bullet reduce the peak pressure in the gun barrel and provide a relatively low pressure adjacent to the muzzle at the time of bullet exit. The improved gun barrel affords increased bullet velocity and accuracy, and reduced felt recoil.
U.S. Pat. No. 4,590,698, incorporated herein by reference, discloses an improved barrel for a firearm or cannon wherein the muzzle velocity of the projectile fired is controlled by systematically bypassing around the projectile during its travel through the barrel of the weapon a portion of gases generated upon firing of the weapon.
U.S. Pat. No. 4,660,312, incorporated herein by reference, discloses a gun barrel having a rifled-bore section at the breech end thereof, the sections having a gas tight connection therebetween, the rifled-bore section comprising a first generally tubular body having a longitudinal bore and at least one spiral groove formed in the wall of the bore to a depth of a predetermined dimension, the rifled-bore section having a length corresponding substantially to the peak pressure point for the gun barrel, the smooth-bore section comprising a second generally tubular body having a longitudinal bore coaxial with the longitudinal bore of the rifled-bore section, and the longitudinal bore of the smooth-bore section having a diameter greater than the diameter of the bore of the rifled-bore section and less than the diameter of the spiral rifling groove.
U.S. Pat. No. 5,841,058, incorporated herein by reference, discloses the construction and arrangement of projectile bearing surface interfaces rearward and forward of a recessed surface chamber of the projectile interface conjointly with the interfaces of bore wall areas segmented by recessed bore chambers which in conjunction effect the deployment/transport/disbursement/development/modulation and transformation of explosive propellant charges sequentially primed and activated rearward and forwardly of the projectile along the bore and in bore wall chambers captively converting high static gas pressure to expansively relieved dynamic propellant gas pressure directly at the projectile reducing firearm barrel recoil while energizing projectile movement along the bore in a closed-system of thermodynamic propellant energy for free flight purposes.
When firing a bullet or projectile from a rifle bore, it is particularly important for the bullet to spiral or spin about its longitudinal axis as it leaves the muzzle. This ensures that the bullet will fly along a straight line through the air to impact its intended target. A problem arises when cartridges are loaded with a bullet wherein the bullet is misaligned relative to the casing. A casing having been loaded in this manner is said to have some degree of runout. For example, as shown in FIG. 1A, a side view of a casing 1 is shown, wherein the casing 3 and the bullet 2 are misaligned. The bullet tip 4 is off the casing longitudinal central axis 5 by a distance, called runout 6. It is much more preferred to have no runout, i.e., the bullet tip 4 is coaxial with the casing longitudinal central axis 5 as shown in FIG. 1B.
Typical, military grade ammunition will have some degree of runout for nearly every cartridge manufactured. For example, a typical .223 caliber cartridge will have runout of as much as 0.09 inches. Cartridges having runout will not produce an accurate shot when fired. When a cartridge is introduced into the breach of a gun, the casing 3 fits snuggly within the breach and therefore becomes coaxially aligned with the central axes of the breach and rifle bore. If the cartridge 1 has some degree of runout, the bullet 2 will be misaligned with the central axes of the breach and rifle bore when the cartridge 1 is introduced into the breach. When a cartridge with some degree of runout is fired in a rifle, the bullet 2 will travel down the rifle bore maintaining its misaligned condition as it travels. When the misaligned bullet 2 exits the muzzle of the rifle and flies through the air, the bullet 2 will spin or rotate around an axis which is different than the longitudinal central axis of the bullet 2. In other words, the bullet 2 will wobble as it flies through the air. This wobble or misalignment in flight causes the bullet to fly off target or deviate from its intended straight line path.
Since typical grade ammunition is manufactured with some degree of runout, there is a need for a rifle bore configuration which aligns the bullet as it travels down the rifle bore.
The present invention is a rifle bore configuration that realigns a bullet as it travels from the breach to the muzzle to ensure that bullets leaving the muzzle spin perfectly without any wobble.
According to one aspect of the invention, there is provided a rifle barrel for realigning a projectile which is propelled through the barrel by gas pressure, the barrel comprising: a bore having a bore diameter through which a projectile may travel; rifling ridges within the bore; and at least one bore expansion chamber in the bore, wherein a diameter of the at least one bore expansion chamber is greater than the bore diameter, wherein a length of the at least one expansion chamber is smaller than an overall length of the projectile and greater than a contact length of the projectile.
According to a further aspect of the invention, there is provided a means of increasing the accuracy of the bullet by purposefully allowing gases to explode past the bullet in order to realign the bullet.
According to still another aspect of the invention, there is provided a process for manufacturing a runout correction rifle barrel, the process comprising: inserting a bore cutting tool into a constant diameter rifle bore; engaging a cutter of the bore cutting tool with a bore of the rifle barrel; and moving the bore cutting tool to remove a portion of the rifle barrel from the bore.
According to a further aspect of the invention, there is provided a process for projecting a projectile from a rifle barrel, the process comprising: increasing gas pressure behind the projectile in the rifle barrel, whereby the projectile is propelled through the rifle barrel; and passing a burst of gas around the projectile, whereby the projectile is aligned coaxially in the rifle barrel.